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sonofcolin

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Is it possible to flush DNS cache for MX records that have been cached by KMS? Can't seem to find this function anywhere.
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peterj

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Are you sure KMS caches this information??

I would imagine that KMS does a lookup every time and that it may just use the O/S cache....?

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sonofcolin

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I'm sure as under stats it says:
DNS resolver statistics:
Total number of MX record queries cached = xx

I know that a mailserver that we send to has changed DNS and our mailserver keeps sending to the old MX record, which bounces back all of our messages. Flushing the cache should clear this.
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sedell

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I have submitted this to Kerio Support in the past. There is no way to clear the cache. It's been filed as a feature request.

I have been told that records are cached for one hour by KMS. If you're not in a rush, you could wait the hour. Otherwise, the only other way is to restart the Kerio service.

Scott
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sonofcolin

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1 hour? This has been on going for 2 weeks!

I know it's a cache problem as the other mailserver logs show that our mailserver is sending to the old MX record.
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sedell

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I was surprised by the one hour response myself. It seems to be much longer... at least for bad records. I've never spent the time to verify a good record in the cache - too much work. Bad records seem to stick around forever though.

Have you tried flushing your machine's DNS cache, and your DNS server (if you use your own). Unfortunately, other than that, a restart of the KMS service is required.

Scott
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peterj

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use the debugging...

send an email to a domain with the dns debugging on and it watch it do a query.

then send another - it will use the cache

then wait an hour and five minutes and it should do the query again...!

I'd be interested to see the results...
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sonofcolin

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Stop and start of KMS seemed to fix it. Just tried a test message and it went through ok.

I would like to know what the official line from Kerio is regarding this. Are queries cached for 1 hour or not?

Thanks for all the suggestions. Peterj, I got your message too late to try your suggestion. I think that would have been conclusive.
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Kerio_jthomas

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Yes, DNS records are cached for the greater value of:

1) TTL set on the record
2) 1 hour

As noted by Scott, we have an open suggestion on this.

Cheers,
Joshua


Joshua Thomas
Technical Support Manager
2350 Mission College Blvd, Suite 400
Santa Clara, CA 95054
Phone: (408) 496-4500
Fax: (408) 496-6902
http://www.kerio.com/support.html

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bperkins

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I have an email that has been stuck in my queue for two days now. I've turned on SMTP logging and DNS logging to try to see what's going on. The only entry I get is this:

[26/Jan/2006 14:39:55][25633] {dns} Searching cache for MX records for host somehost.com
[26/Jan/2006 14:39:55][25633] {dns} Searching cache for A records for host somehost.com

It doesn't say anything about finding it in the cache or polling the DNS servers to find it. Using the same DNS servers as my mailserver, I can ping the recipient mailserver just fine. I absolutely hate restarting the mailserver, but is this the only option as of KMS 6.1.2?

Thanks,
Brian
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cohcon

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Just because it's habit for me, from the mailserver cmd line can you run "nslookup -q=mx <somehost.com>" and get valid results?

It may help rule out something weird with the dns.

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bperkins

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yep, I forgot to mention the server in question does have an A record, but no MX record. From the command line on the server itself, it will find the A record just fine.

I guess I'll need to restart KMS tonight to flush the cache.....AAARRRGGG.

Thanks for the help cohcon!
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cohcon

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No problem, glad to help.

Conn


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